Cisco A9K-SIP-700 Configuration Guide

You can configure BFD to detect roundtrip latency on non-bundle interfaces using the echo latency detect
command beginning in Cisco IOS XR 4.0.1.
Time (T): Echo#1 TX (count = 1)
T + 1 ms: Echo#1 RX (count = 0)
T + 50 ms: Echo#2 TX (count = 1)
T + 51 ms: Echo#2 RX (count = 0)
T + 100 ms: Echo#3 TX (count = 1)
T + 150 ms: Echo#4 TX (count = 2)
T + 151 ms: Echo#3 RX (count = 0; ~50 ms roundtrip latency)
T + 200 ms: Echo#5 TX (count = 1)
T + 250 ms: Echo#6 TX (count = 2)
T + 251 ms: Echo#4 RX (count = 0; ~100 ms roundtrip latency)
T + 300 ms: Echo#7 TX (count = 1)
T + 350 ms: Echo#8 TX (count = 2)
T + 351 ms: Echo#5 RX (count = 0; ~150 ms roundtrip latency)
T + 451 ms: Echo#6 RX (count = 0; ~200 ms roundtrip latency; no failure detection)
T + 501 ms: Echo#7 RX (count = 0; ~200 ms roundtrip latency; no failure detection)
T + 551 ms: Echo#8 RX (count = 0; ~200 ms roundtrip latency; no failure detection)
Note
Looking at the delay between receipt of echo packets for the BFD session, observe that no latency is beyond
the (I x M) window:
Echo#1 RX – Echo#2 RX: 50 ms
Echo#2 RX – Echo#3 RX: 100ms
Echo#3 RX - Echo#4 RX: 100ms
Echo#4 RX - Echo#5 RX: 100ms
Echo#5 RX - Echo#6 RX: 100ms
Echo#6 RX - Echo#7 RX: 50ms
Echo#7 RX - Echo#8 RX: 50ms
Summary of Packet Intervals and Failure Detection Times for BFD on Bundle Interfaces
For BFD on bundle interfaces, with a session interval I and a multiplier M, these packet intervals and failure
detection times apply for BFD asynchronous mode (Table 3: BFD Packet Intervals and Failure Detection
Time Examples on Bundle Interfaces):
•
Value of I—Minimum period between sending of BFD control packets.
•
Value of I x M
◦
BFD control packet failure detection time.
◦
Minimum period between sending of BFD echo packets.
The BFD control packet failure detection time is the maximum amount of time that can elapse without receipt
of a BFD control packet before the BFD session is declared down.
• Value of (I x M) x M—BFD echo packet failure detection time. This is the maximum amount of time
that can elapse without receipt of a BFD echo packet (using the standard multiplier counter scheme as
described in Echo Packet Failure Detection In Asynchronous Mode) before the BFD session is declared
down.
Cisco ASR 9000 Series Aggregation Services Router Routing Configuration Guide, Release 5.1.x
182 OL-30423-03
Implementing BFD
BFD Packet Information

Cisco A9K-SIP-700 Specifications

General

Brand	Cisco
Model	A9K-SIP-700
Category	Network Router
Language	English